1. Field of the Invention
The present invention relates to a super bright light emitting diode (LED), and more particularly to an LED having a nanorod (or, nanowire) structure and its manufacturing method.
2. Description of the Related Art
LED is generally used as a simple display element of a gauge or meter at the early state, and recently noticed as a full-color display element having super brightness, high contrast and long life cycle owing to the development of blue and green super brightness LED. On the other hand, as a material of such an LED, a III-nitrogen compound semiconductor using such as GaN is recently researched abundantly since III–V group nitride semiconductors have so wide a bandgap to give a light in the almost all wavelengths from visible rays to ultraviolet rays according to composition of nitride. However, GaN currently uses a sapphire substrate since there is no lattice-matched substrate at present, so there is still much mismatching and coefficient of thermal expansion is still great.
Thus, there is proposed a conventional laminated-film LED in which a n-GaN layer to which n-type impurities are added, an InGaN activate layer, and a p-GaN layer to which p-type impurities are added are subsequently laminated on a sapphire substrate. However, the laminated-film LED has a limit in the element performance (or, brightness) since many threading dislocations exist due to the lattice mismatching, caused by the aforementioned properties and growth manners of GaN. In addition, the conventional laminated-film GaN LED suffers from some limitations such as the poor extraction efficiency of light, the wide spectral width, and the large divergence of the output as well as the aforementioned threading dislocations, in spite of many advantages of being relatively simple to design and manufacture and having low temperature sensitivity.
On the other hand, in order to overcome the disadvantages of the laminated-film LED, a nano-scale LED which forms an LED by making a p-n junction with the use of one-dimensional rod or linear nanorod (or, nanowire), or a micro-scale LED using micro-ring or micro-disc is studied. However, there is unfortunately found that many threading dislocations are generated in such a nano-scale or micro-scale LED similar to the laminated-film LED, so an LED having super brightness to a satisfactory level is not still appeared. In addition, the nanorod LED is a simple p-n junction diode, not giving super brightness. Moreover, the micro-ring or micro-disc LED is currently manufactured using photolithography or electron-beam lithography which is apt to damage the lattice structure of GaN during the lithography process, so brightness and light emission efficiency of the LED are not satisfactory.